Optical-interference microphone

Abstract

An optical-interference microphone having a high sensitivity and bandwidth, and that is suitable to be manufactured by micromachining techniques. The microphone includes a back member, a diaphragm and an air gap formed between the back member and diaphragm. Further, the diaphragm includes a plurality of holes. The microphone utilizes optical interference to sense the sound-induced motion of the diaphragm. A light source and detector can be included as components of the microphone or can be at a remote location and connected to the microphone with an optical fiber.

What is claimed is:  
     
       1. An article comprising a microphone to be referred to as an optical-interference microphone comprising: 
       a) a first layer comprising a material that is substantially transmissive for electromagnetic radiation of wavelength λ;  
       b) a second layer comprising a material that is substantially transmissive for said electromagnetic radiation, the first and second layers being spaced apart and defining a gap volume between said first and second layers;  
       c) at least one of the first and second layers comprising a plurality of through-holes disposed therein such that said gap volume is in pneumatic communication with an ambient atmosphere having a pressure, such that a spacing between said first and second layers varies in response to changes in the ambient atmosphere pressure;  
       d) the article further comprising a source of said electromagnetic radiation of said wavelength λ and a detector for detecting said electromagnetic radiation of said wavelength λ, said source and detector being disposed such that at least a portion of said electromagnetic radiation of said wavelength λ that is emitted by said source is transmitted through said gap volume and impinges on the detector, with an intensity of the impinging electromagnetic radiation being responsive to the variations in the spacing between the first and second layers.  
     
     
       2. Article according to  claim 1 , wherein said source of electromagnetic radiation is spaced from the optical-interference microphone, with said electromagnetic radiation being transmitted to the said microphone through a first optical fiber. 
     
     
       3. Article according to  claim 2 , wherein said detector is spaced from the optical-interference microphone, and said electromagnetic radiation is transmitted from said microphone to the detector through at least a portion of the first optical fiber. 
     
     
       4. Article according to  claim 2 , wherein the article further comprises an optical fiber coupler for separating the electromagnetic radiation that is propagating through the first optical fiber from the source of electromagnetic radiation to the optical-interference microphone from the electromagnetic radiation that is propagating through the first optical fiber from said microphone towards the detector. 
     
     
       5. Article according to  claim 1 , wherein at least one of the source of electromagnetic radiation and the detector are disposed on the optical-interference microphone. 
     
     
       6. Article according to  claim 1 , wherein said changes in the ambient atmosphere pressure are an acoustical signal. 
     
     
       7. Article according to  claim 1 , wherein said detector is spaced from the optical-interference microphone, with said electromagnetic radiation being transmitted from said microphone to the detector through optical fiber. 
     
     
       8. Article according to  claim 1 , wherein at least one of said first and second layers consists of material selected from the group consisting of silicon and silicon nitride.